基于GaN HEMT的半桥LLC优化设计和损耗分析

Optimal Design and Loss Analysis of Half-bridge LLC Converter Based on GaN HEMT

较之于传统硅器件,新出现的增强型氮化镓晶体管GaN HEMTs(gallium nitride high electron mobility transistors)具有很高的开关速度和高功率密度的特性,可以为直流变换器提供有效的改进。为了解决GaN HEMT在硬开关应用场合下的波形振荡并提高功率密度和效率,采用半桥LLC谐振变换器为本次应用的拓扑结构。以减小损耗为目的,优化了LLC的谐振参数和死区时间。在400 V输入电压、开关频率300 kHz和输出电压18 V电流12 A的测试条件下,效率达到95.59%。最后对变换器的损耗来源进行分析,损耗的理论计算值接近实际测量值,证明了方法具有一定的实用性。

Compared with the traditional silicon devices, the newly emerged E-mode gallium nitride high electron mobility transistors(GaN HEMTs) feature ultrafast switching speed and high power density, providing effective improvements for DC converters. To reduce the waveform oscillations of GaN HEMT in the hard-switching application and improve the power density and efficiency, a half-bridge LLC resonant converter is adopted as the topology under this application scenario. For the purpose of reducing loss, the resonant parameters and dead time of LLC are optimized. Under the test condition of 400 V input voltage, 300 kHz switching frequency, 18 V output voltage and 12 A output current, the efficiency reached 95.59%. Finally, the loss sources of the converter were analyzed, and the value of theoretical calculation was close to that of the actual measurement, showing the practicability of the proposed method.